Moan most likely is coming from the shaft being slightly out of balance or excessive pinion angle. Pinion angle you can test at home by playing with the caster cams (within reason). While you're down there, go ahead and grease your driveshaft (search the forum, tons of info on this). If those 2 things do not solve the problem, take it to a GOOD driveline shop and have them work their magic.
Whys that?If your gonna go custom , get a double doube Cardon. One on each end.